Automatic level control for metal casting



p 6 J. WOODBURN, JR- 3,340,925 I AUTOMATIC'LEVEL CONTROL-,F'OR METALCA$TING Original Filed Dec. 1963 3 Sheets-She t I Sept-12,1967 J.WOODBURN, JR 3,340,925

' AUTOMATIC LEVEL CONTROL FOR METAL, CASTING Original Filed Dec. 196-1 3Sheets-511 1 Sept. 12, 1967 Original Filed Dec. i,

J. WOODBURN, JR

AUTOMATIC LEVEL CONTROL FOR METAL; CASTING 3 Sheets-Quad 3 Ja/wesPatented Sept. 12, 1967 AUTOMATIC LEVEL CONTROL FOR METAL CASTING JamesWoodburn, Jr., Wheaton, Ill., assignor to Amsted IndustriesIncorporated, Chicago, 11]., a corporation of New Jersey Originalapplication Dec. 3, 1963, Ser. No. 327,642, now Patent No. 3,287,773,dated Nov. 29, 1966. Divided and this application Apr. 6, 1966, Ser. No.540,659

1 Claim. (Cl. 164281) ABSTRACT OF THE DISCLOSURE In a continuous castingarrangement, a mold having a bottom opening is associated with a ladleand pressure is imposed on the molten metal in the ladle for forcing itupwardly into and through the mold. Control means is provided,responsive to the weight of the ladle and the metal in the ladle, forcontrolling the development of air pressure in the ladle as the moltenmetal is forced from the ladle through the mold.

This application is a division of my copending application Ser. No.327,642, filed Dec. 3, 1963, now Patent No. 3,287,773.

The present invention relates generally to metal casting, and moreparticularly to continuous upcasting involving pressure pouring whereina mold having a bottom pouring opening is associated with a ladle, andpressure is imposed on the molten metal in the ladle for forcing itupwardly into and through the mold.

It is, of course, desired to maintain the flow or movement of the moltenmetal into the mold at a certain predetermined rate to accommodatewithdrawal of the cast product at a similarly constant rate. In thisoperation, it is desired to maintain the molten portion of the metal inthe mold at a certain height relative to the freezing and castingfunction therein. As the cast article is withdrawn continuously, ittends to lessen the height of the molten portion of the metal in themold, but the air pressure imposed on the molten metal in the ladleforces the molten metal into the mold and tends to raise that height,that height under ideal conditions remaining constant.

A broad object of the invention is to provide novel means for sensingthe change in level of the molten metal in a ladle to enable theoperator to perform corresponding manipulations, such as additionalpouring, or to per-' form other functions and controls, either manual orautomatic.

A more specific object is to provide means for sensing such level bysensing the weight of the molten metal.

Still another object is to provide a novel method of casting of thecharacter set out above.

Other objects and advantages of the invention will appear from thefollowing detailed description taken in conjunction with theaccompanying drawings in which:

FIGURE 1 is a vertical sectional view of casting apparatus embodying theprinciples of the invention, certain portions thereof such as thecontrols being shown dia grammatically;

FIGURE 2 is a face view of one form of indicating device utilized in theapparatus;

FIGURE 3 is a side view of the apparatus of the instrument of FIGURE 2;

FIGURE 4 is a diagrammatic view of one form of control device;

FIGURE 5 is a diagrammatic view of another form of control device; and

FIGURE 6 is a vertical sectional view of a modified form of castingapparatus.

Referring now in detail to the accompanying drawings, attention isdirected first to FIGURE 1 which includes a tank 10 including areceptacle 12 and a cover 14 detachably mounted thereon in sealingrelation thereto to confine air pressure in the tank. The detailedstructure of the tank may be as desired. A ladle 16 is mounted in thetank on load cells 18 which are weight sensing means, functioning tosense the weight of the ladle for use in conjunction with correspondingindicating means. As will be described more fully hereinbelow, theweight of the ladle and the molten metal therein can be utilized forindicating the quantity of molten metal therein by subtracting the emptyweight of the ladle from the gross weight sensed by the load cells. Theladle 16 may be of conventional form, made of insulating refractorymaterial and, if desired, may have an induction heating coil 20 embeddedin the wall therein for heating the molten metal 22 or maintaining it ina molten condition. y

The ladle 16 may be inserted in the tank receptacle 12, after theremoval of the cover 14 therefrom, by suitable means such as a crane,after which the cover is replaced and sealed on the receptacle. Thecover 14 is incorporated in an assembly 24 which includes a pouring tube26 and a mold 28. The tube 26 is mounted in the cover by suitable meansin sealed relation thereto, and it extends downwardly into closeproximity to the bottom of the ladle. The tube extends to andcommunicates with the mold, the mold having a central passage 30 thereinforming a cavity. This passage or cavity, as will be noted, opensthrough both the bottom and top of the mold, the molten metal beingforced into the mold through the bottom and the cast product beingwithdrawn upwardly therefrom through the top opening. Preferably, theinner diameter of the pouring tube is equal to the diameter of thecavity.

The mold 28 includes a sleeve 32 forming the cavity which may be of suchmaterial as graphite. Surrounding the sleeve is a cooling jacket 34 ofsuitablehigh heat conducting material such as copper, and having anannular space 36 therein for circulation of cooling medium such aswater. This cooling medium may be injected through an inlet pipe 38 froma supply source (not shown) and ejected through an outlet conduit 40.

The cast product here indicated at 42 is in the form of a tube or pipe,and to produce such tubular product, the product is withdrawn at apredetermined rate relative to the rate of flow of the molten metal intothe mold, together with other factors, e.g., temperatures involved. Thecast product, after initiation of its removal, is continuously withdrawnby friction rollers 44 engaging it and rotating in the directionsindicated.

The molten metal 22 is forced upwardly through the pouring tube 26 byair pressure produced in the sealed tank 10. It will be understood thatfor a given pressure the molten metal will stand at a given level in themold, and as the cast product is continuously removed, the level of themolten portion of the metal tends to lower and would lower if thepressure should remain constant. In order, therefore, to continue thepouring operation, additional pressure is produced in the tank, tomaintain the level of the molten metal in the mold, because as themolten metal in the tank is depleted and the level thereof lowers,maintaining the level of the column in the mold is equivalent to raisingthe height of the column, i.e., the height of the column above the levelin the ladle increases; hence the greater air pressure.

Air is introduced into the tank from a suitable source (not shown)through an inlet conduit 46 which includes a throttling control valve 48of known type. Air is exhausted from the tank through an outlet conduit50 having a control valve 52 therein of suitable and known type. Thevalves 48 and 52 may be controlled manually when the apparatus is undermanual operation, and controlled automatically when the apparatus isunder automatic control, as described below.

As indicated above, the load cells 18 sense the weight of the ladle andthe contents thereof, or the molten metal therein. This sensingoperation may be utilized for use in any of a variety of differentfunctions or control manipulations. In the simplest form of theoperation of the apparatus, means utilized for indicating the weight ofthe ladle as sensed by the load cells, and the operator performsoperations in accordance therewith. The load cells are so constructed,and the indicating means so calibrated, as to indicate the weight of themolten metal in the ladle as a resultant of effectively deducting theempty weight of the ladle from the gross weight sensed and thus indicatethe quantity thereof. This indication made by the visual indicatorsenables the operator to determine whether to continue'pouring, forexample, or to replenish the molten metal, etc. For example, theoperator knows the quantity of metal required for a single pouringoperation, and if the visual indicating means indicates that sufficientmolten metal remains in the ladle for that purpose, he can effect such apouring operation, while on the other hand when he notes that there isinsufficient molten metal for that purpose, he will arrange for anotherand full ladle to be put in place.

Instead of providing merely visual indications for guiding the operator,the apparatus may be used for directly effecting control operations inaccordance with the conditions sensed. For example, the load cells 18may be incorporated in an arrangement of control instruments forautomatically performing the necessary or desired control operations,such as developing air pressure in the tank to raise the level of themolten metal in the mold directly proportional to the removal of themetal in the form of the cast article, whereby to automatically maintainthe supply of molten metal in the mold at the desired level to enablewithdrawal of the cast article at the desired rate. The principalconsideration of the apparatus is that the weight of the ladle, and morespecifically the Weight of the molten metal therein, is utilized fordetermining the quantity of molten metal thereof to enable either suchmanual manipulations as stated or to effect any such automaticmanipulations as are desired.

The load cells 18 may be in the form of mechanical scales, for example,and utilized with a visual indicator 60 (FIG. 2) in which a band orpointer 64 mounted on a shaft 66 sweeps over a dial 62 and in doing soindicates the weight and hence quantity of molten metal in the ladle.

In the case of automatic control of the apparatus, the control valves 48and 52 are controlled respectively through suitable lines ofcommunication 54, 56, which may be electrical lines or cables forcontrolling electric instrumentalities which, in turn, control thevalves 48 and 52 in a known manner. The exact construction of the valvesand their control means may be any of various kinds, whether electricalor otherwise, and may if desired be mechanically, pneumatically, orhydraulically controlled or operated, etc. All of these forms are wellknown, and may be selected according to the practical circumstancessurrounding any given installation.

The source of control of the valves is an instrumentality 58 heredesigned simply a controller, itself controlled by the load cells 18.The controller 58 is of suitable type according to the character of thevalves, such as electrical, mechanical, etc.

The instrument 60 is adapted for use in automatic control, as well asmanual control. An arm 68 is mounted on a sleeve 70 having a hand knob72 friction-fitted on the shaft 66 and normally rotated with it, butcapable of being manually rotated relatively to the shaft, and therebyset thereon. The arm is in position for engaging electrical contacts 76upon swinging of the arm upon rotation of the shaft. Upon engagement ofthese contacts, a circuit is established through wires 78 forcontrolling the control apparatus which may be a shuttingoif operation.

Automatic means for supplying additional air upon depletion of theliquid level may be of any suitable and known type. For example, inreferring to FIGURE 4, an arm 80 is mounted on the shaft 66 for swingingmovement therewith. The arm 80 is connected at one end with anelectrical conductor 82, and its other end is positioned forsuccessively engaging contacts 84 connected with conductors 86. Theconductors lead to instrumentalities 88 which are pressure-sensitivedevices operating on the basis that upon existence of a predeterminedpressure, a control function will be performed. In the present instance,these pressure-sensitive devices 88 are connected with the interior ofthe tank so as to function in response to the pressure therein. As thearm sweeps in response to depletion of the molten metal in the ladle, assensed through the load cells 18, they successively put into circuitcorresponding ones of the pressure-sensitive devices. Thesepressure-sensitive devices thereupon control one or both of the valves48 and 52 for maintaining the pressure in the tank at the valvecontrolled by the characteristics of the pressuresensitive devices.

It should be understood that satisfactory operation may be achieved bycontrolling the air pressure in the tank in steps, that is the airpressure may be increased in infinitely small or relatively largeincrements. Notwithstanding the foregoing, it is also contemplatedwithin the scope of the invention that gradual or infinitely variablecontrol devices may be utilized, as indicated above, instead of theapparatus illustrated in FIGURE 4. Such arrangement may include, forexample, a progressively advancing device such as the rhcostat 88 ofFIG. 5, or a coil and armature movable therein, or other pneumatic,hydraulic, or mechanical devices.

The load cells 18 sense only the ladle and the molten metal thereinbelow the level thereof, and not the metal in the column in the pouringtube above the level of the metal in the ladle. The air pressure in thetank is imposed on the ladle and the molten metal therein in alldirections so that a pressure balance exists. As the level in the ladlelowers, the column in the pouring tube thereabove, which increases, isnot sensed by the load cells, the weight of this column reacting throughthe metal in the ladle which in turn produces back pressure on the airin the tank. The differential in air pressure as determined by the levelin the ladle is proportioned to the height of the column in the pouringtube above the level in the ladle.

The foregoing tank and ladle apparatus is designed for batch type ofoperation. However, the invention is sufficiently broad to covercontinuous replenishment. This may be done through a filling tube 90which is mounted in the cover 14 and extends down to a point adjacentthe bottom of the ladle. This pouring tube is at least as high as thetop of the mold. The molten metal rises in the filling tube tosubstantially the same height as that in the mold, and in the normaloperation the metal does not flow out of the filling tube in response tothe air pressure produced in the tank. As the molten metal is depletedin response to the casting operation, and in the absence ofreplenishment, the air pressure in the tank is increased in the mannerdescribed above. However, it is possible to continuously replenish theladle by pouring into the filling tube, and in this case the airpressure may be maintained constant and the rate of filling iscontrolled so as to maintain the level in the mold at the desiredheight. It is also possible to utilize a combination of the functions,namely control the air pressure for maintaining the desired height inthe mold without filling, and then when it is desired to replenish theladle, such may be done through the filling tube and in this operationthe value of the air pressure is controlled to compensate for thefilling operation to maintain the level constant in the mold.

While I have disclosed certain preferred forms of the invention, it willbe understood that changes may be made within the scope of the appendedclaim.

I claim:

Apparatus for continuous casting of metal comprising a sealed tank, aladle in the tank adapted to contain molten metal, a mold having abottom opening mounted on said tank, a pouring tube communicatingbetween the ladle and the mold, the arrangement being operative inresponse to development of air pressure in the tank for forcing moltenmetal from the ladle through the pouring tube into the mold, means fordeveloping air pressure in said tank, means for withdrawing the castarticle from the mold while the molten metal is forced into the mold,and means responsive to the Weight of the ladle and the molten metaltherein for controlling the development of air pressure in the tank inresponse to depletion of the molten metal in the mold pursuant toremoval of the cast article.

References Cited UNITED STATES PATENTS 2,753,605 7/1959 Carleton 22 s52,905,989 9/1959 Black 22-49 2,922,205 1/1960 Deakin et a1. 22 79 102,990,592 7/1961 Hursen 22- 79 J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

